C/O Spring - 3.50 ID x 10 350# Silver P/C

The QA1 C/O Spring - 3.50 ID x 10 350# Silver P/C is a precision-engineered coil-over suspension spring designed for serious vehicle builders and performance enthusiasts seeking tunable ride quality and load control. Built by QA1, a trusted manufacturer in the competition and street performance space, this single coil-over spring delivers consistent spring rates across a wide range of compression, making it ideal for custom chassis builds, drag racing platforms, and street machines where suspension geometry demands precise load management. Whether upgrading an existing coil-over system or designing a complete custom suspension, this 350 lb/in spring rate provides the stiffness necessary for responsive handling without sacrificing adjustability.

This coil-over spring features a 3.50-inch upper inner diameter that mates with standard coil-over mounting hardware, a 10-inch free length, and a 350-pound-per-inch spring rate that balances preload range with progressive engagement characteristics. The silver powder-coat finish resists rust and UV degradation, maintaining appearance while protecting the high-carbon steel construction against corrosion—critical for long-term reliability in both street and competition environments. The single pigtail design ensures proper seating within standard shock bodies and allows for straightforward installation without binding or misalignment issues that can compromise suspension geometry or accelerate wear on dampers.

This spring is best suited for builders working with diameter-specific coil-over kits where upper ID compatibility is non-negotiable—common in tube-frame chassis, independent front suspension (IFS) conversions, and purpose-built race cars. Installation requires a spring compressor and knowledge of preload adjustment to maximize ride height range and maintain suspension clearance during full compression cycles. The 350 lb/in rate pairs well with modern adjustable dampers and works across a spectrum of vehicle weights; verify your chassis or kit specifications to ensure the 3.50-inch ID and 10-inch length align with your shock tower geometry and suspension travel requirements before purchase.